Operation of switches, protective devices (e.g., circuit breakers, fuses, electromechanical and solid state relays), contactors, motor overload circuits, and electronic monitoring and control devices (e.g., microcontrollers, data acquisition and control systems) (hereinafter “components”) can be affected by changes in the surrounding environment in which these components are disposed. For example, if the components are disposed in an enclosure and the relative humidity of the components' surrounding environment increases and/or interior temperature decreases beyond a certain threshold, thereby causing water condensation thereon, the components may not operate as intended and/or an arc fault condition may occur. Typically, the conditions of the components' surrounding environment are usually apparent when a person opens the enclosure to observe its inside. However, these conditions are not noticed until the enclosure is opened and the components' surrounding environment can be observed. While the components operate to prevent potentially harmful situations, the failure to acknowledge and adjust the components' surrounding environment can lead to other hazardous consequences, such as harm to equipment and/or personnel. Many of these components can be expensive and/or critical to commercial/industrial plant operation and/or personnel safety. If the change in the components' surrounding environment is not properly monitored and controlled, then the expensive and/or critical components can become damaged and/or not operate as intended when the surrounding environment is outside of acceptable operating conditions. Expensive and/or critical equipment that the expensive and/or critical components protect also can become damaged. In addition, replacement of the environmentally damaged expensive and/or critical components can be expensive and time consuming. Generally a heating element is provided in the enclosure that is activated when an interior temperature falls below a temperature set point and/or relative humidity exceeds a relative humidity set point.
Back-up battery operation of the aforementioned electronic monitoring and control devices, and critical interfaces whose states must be maintained during power interruption may also be included in the enclosure. Provision for charging and testing of the back-up battery must also be provided with the control. A battery charger for charging the battery and a resistive load for testing the load capabilities of the battery, e.g., voltage drop under load conditions, are provided in the control enclosure and/or external to the control enclosure.
Providing separate devices for space heating and battery load testing require expensive and space consuming high power resistance elements, wires within a harness to accommodate the heating elements, and control circuits therefore, and a significant amount of space either inside of the enclosure or in another enclosure adjacent thereto.